Hemimycale columella (Bowerbank, 1874)


Family : Hymedesmiidae

Form: Thin sheet to cushion.

Colour: Bright red to pale orange or pink. The darker coloured depressions have lighter coloured rims.

Smell: None.

Consistency: Moderately soft when alive and undisturbed.

Surface: Slippery, smooth. The surface is covered in shallow, circular, non-contractile depressions of varying diameters. The rims are usually lighter coloured than the rest of the body. The depressions contain the inhalent pores, and are covered by a fine, gauze-like, mesh. These depressions become less obvious when the sponge is left out of the water.

Apertures: Oscules occur infrequently. They are located on top of special papillae which contract if disturbed and are lost on preservation.

Contraction: Noticeable. In particular the oscules cease to be obvious when the sponge is removed from the water. "Cushion tends to curl up at the edges when preserved."

Internal characters

Skeleton: Plumose. The main skeleton is of loose fibres of spicules, which run vertically up to the surface, branching and anastomosing. There is no special ectosomal skeleton.

Spicules: The megascleres are anisostrongyles (i.e. strongyles with unequal ends), sometimes modified to styles to subtylostyles. These measure 300-(330)-345Ám in length by 6-8Ám in width. There are no microscleres.

Habitat: A common species, found on clean rock, "stones or shingle". It attains its optimal development in the kelp zone. Apparently not found in harbours.

Distribution: "Arctic; British Isles; France; Mediterranean." Not North Sea coasts. Northern limit probably is the west coast of Scotland.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: Provided the colour is red-pink and the rims of the depressions are of a lighter colour, the identification stands a good chance of being correct, but in case of doubt microscopic examination is essential. Several other genera contain species which have depressions with rims which are the same colour as the general surface (see e.g. Phorbas fictitius and Hymedesmia paupertas in this Guide).

Voucher: BELUM : Mc1258. Rathlin Is, Antrim.

Editors: J.D. Guiterman, D. Moss, B.E. Picton.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland